Analysis of kinetics of diffusion induced recrystallization in Fe phase of Cu/Fe/Cu diffusion couples

Abstract

Combining the columnar-geometry and boundary-diffusion model by Li and Hillert with the energy balance model by Kajihara and Gust, a new kinetic equation has been obtained to describe the growth rate of the alloyed region due to diffusion induced recrystallization (DIR) in a solution phase of binary systems The equation has been utilized to analyze quantitatively the kinetics of DIR in the Fe(Cu) system observed by the present authors using Cu/(Fe-4.8mass%)/Cu diffusion couples. The notation Fe(Cu) means that Cu atoms diffuse into a pure Fe or binary Fe-Cu phase. The observations indicate that the thickness l of the DIR region formed in the Fe phase from each interface increases with increasing annealing time t according to the relationship l=1.58 × 10-6(t/t0)0.29 at 1 323 K. Here, l and t are measured in m and s, respectively, and t0 is unit time, 1 s. Using the mobility M as the fitting parameter of the kinetic equation, we have obtained the value of M = 8.64 × 10-13m4/Js and the relationship l = 1 08 × 1(T6(f/fo)0.33 on the basis of the observations. Through the analysis, it is concluded that l increases in proportion to √t for DIR in a pure metal whereas l increases proportionately with 3√t for DIR in a solution phase even with a low solute concentration.